This invention relates to the field of micromirror manufacturing systems, more particularly to alignment of micromirrors and micromirror packages.
Micromechanical devices are small structures typically fabricated on a semiconductor wafer using techniques such as optical lithography, doping, metal sputtering, oxide deposition, and plasma etching which have been developed for the fabrication of integrated circuits.
Micromirrors are a type of micromechanical device. Other types of micromechanical devices include accelerometers, pressure and flow sensors, gears and motors. While some micromechanical devices, such as pressure sensors, flow sensors, and micromirrors have found commercial success, other types have not yet been commercially viable.
Micromirrors are primarily used in optical display systems. In display systems, the micromirror is a light modulator that uses digital image data to modulate a beam of light by selectively reflecting portions of the beam of light to a display screen. While analog modes of operation are possible, commercially feasible micromirrors typically operate in a digital bistable mode of operation and as such are the core of the first true digital full-color image projection systems.
Micromirrors have evolved rapidly over the past ten to fifteen years. Early devices used a deformable reflective membrane which, when electrostatically attracted to an underlying address electrode, dimpled toward the address electrode. Schlieren optics illuminate the membrane and create an image from the light scattered by the dimpled portions of the membrane. Schlieren systems enabled the membrane devices to form images, but the images formed were very dim and had low contrast ratios, making them unsuitable for most image display applications.
Later micromirror devices used flaps or diving board-shaped cantilever beams of silicon or aluminum, coupled with dark-field optics to create images having improved contrast ratios. Flap and cantilever beam devices typically used a single metal layer to form the top reflective layer of the device. This single metal layer tended to deform over a large region, however, which scattered light impinging on the deformed portion. Torsion beam devices use a thin metal layer to form a torsion beam, which is referred to as a hinge, and a thicker metal layer to form a rigid member, or beam, typically having a mirror-like surface: concentrating the deformation on a relatively small portion of the micromirror surface. The rigid mirror remains flat while the hinges deform, minimizing the amount of light scattered by the device and improving the contrast ratio of the device.
Recent micromirror configurations, called hidden-hinge designs, further improve the image contrast ratio by fabricating the mirror on a pedestal above the torsion beams. The elevated mirror covers the torsion beams, torsion beam supports, and a rigid yoke connecting the torsion beams and mirror support, further improving the contrast ratio of images produced by the device.
Micromirror arrays used in display systems are small compared to most other technologies. The small array size makes the alignment of the array critical to the performance of the device. A misalignment of only 100 xcexcm shifts the image more than eight image pixels. While this misalignment requires larger, more expensive optics in sequential color systems that use a single micromirror, misalignment can complicate the convergence operation in the larger three-micromirror display systems. The micromirror package are used to align the micromirror array to the display system optics. Not only must the micromirror be precisely aligned relative to the package, the plane of the micromirror must be aligned with the plane of the projection lens to achieve proper focus across the entire micromirror array. What is needed is a method and system of ensuring precise alignment of the micromirror array within a micromirror package.
Objects and advantages will be obvious, and will in part appear hereinafter and will be accomplished by the present invention which provides a method and system for precision micromirror positioning. One embodiment of the claimed invention provides a method of mounting a micromirror array on a package substrate, the method comprises: providing a package substrate, the package substrate having at least two edges and one surface; aligning the package substrate along an y axis by contacting the package substrate in two predefined regions along a first edge; aligning the package substrate along an x axis by contacting the package substrate in one predefined region along a second edge; aligning the package substrate along a z axis by contacting the package substrate in three predefined regions along a first surface, said x, y, and z axes being orthogonal and the first surface being parallel to the x and y axes; and attaching a micromirror at a predetermined position on the package substrate.
Another embodiment of the present invention provides a method of aligning a micromirror array to a display system. The method comprises: providing a package substrate, the package substrate having at least two edges and one surface; aligning the package substrate along an y axis by contacting the package substrate in two predefined regions along a first edge; aligning the package substrate along an x axis by contacting the package substrate in one predefined region along a second edge; aligning the package substrate along a z axis by contacting the package substrate in three predefined regions along a first surface, said x, y, and z axes being orthogonal and the first surface being parallel to said x and y axes; attaching a micromirror at a predetermined position on the package substrate; attaching a cover to the package substrate to enclose the micromirror; providing a display system having a socket to hold the micromirror; and placing the package substrate in the socket such that the socket aligns the package substrate by contacting the package substrate in the two predefined regions along the first edge, the one predefined region along the second edge, and the three predefined regions along the first surface.
Another embodiment of the disclosed invention provides a method of mounting a micromirror array on a package substrate. The method comprising: providing a package substrate, the package substrate having at least two edges and one surface; aligning the package substrate along an y axis by contacting the package substrate in two predefined regions along a first edge; aligning the package substrate along an x axis by contacting the package substrate in one predefined region along a second edge; and attaching a micromirror at a predetermined position on the package substrate.
Another embodiment of the present invention provides a method of aligning a micromirror array to a display system. The method comprising: providing a package substrate, the package substrate having at least two edges and one surface; aligning the package substrate along an y axis by contacting the package substrate in two predefined regions along a first edge; aligning the package substrate along an x axis by contacting the package substrate in one predefined region along a second edge; attaching a micromirror at a predetermined position on the package substrate; attaching a cover to the package substrate to enclose the micromirror; providing a display system having a socket to hold the micromirror; and placing the package substrate in the socket such that the socket aligns the package substrate by contacting the package substrate in the two predefined regions along the first edge, the one predefined region along the second edge, and the three predefined regions along the first surface.
Another embodiment of the disclosed invention provides a method of mounting a micromirror array in a display system. The method comprising: providing a micromirror array in a package, the package having at least two edges and one surface; aligning the package along an y axis by contacting the package substrate in two predefined regions along a first edge; and aligning the package along an x axis by contacting the package in one predefined region along a second edge.
Another embodiment of the disclosed invention provides a method of aligning a micromirror array to a display system. The method comprising: providing a micromirror package, the package having at least two edges and one surface; aligning the package along an y axis by contacting the package in two predefined regions along a first edge; aligning the package along an x axis by contacting the package in one predefined region along a second edge; and aligning the package along a z axis by contacting the package in three predefined regions along a first surface, the x, y, and z axes being orthogonal and the first surface being parallel to the x and y axes.